In the scrubbing of converter gases containing calcium-oxide particles and carbon dioxide with water it is a standard practice to recirculate the scrubbing water and then to settle out the particles, decanting and recycling the liquid. Fresh water is added to the wash water to make up losses.
A particular problem with such arrangements is that dust particles and calcium deposit in the water-recirculating system. These deposits are a result of the fact that the calcium-oxide particles picked up by the wash water form soluble calcium hydroxide which dissolves. The calcium ion combines with the carbon dioxide in the water to form insoluble calcium carbonate (CaCO.sub.3).
It has been attempted to avoid these deposits by adding products to the water which ensure the precipitation of the dissolved calcium in the form of insoluble calcium compounds prior to recirculation. The additives necessary to accomplish this are relatively expensive and must be used in relatively large quantities, i.e., at least stoichiometrically equivalent to the calcium content of the gas treated. Approximately 75% of the wash water must be replaced with fresh water in conventional systems. Obviously such a system leads to further difficulties in the disposal of the contaminated wash water and the supply of the necessary large quantities of fresh water.